lipid
(rus. липид)
— lipid may be broadly defined as a hydrophobic organic substance soluble in organic solvents; according to the rigorous chemical definition, it is a hydrophobic or amphiphilic molecule, obtained by condensation of thioesters or isoprenes.

Description

Lipids are one of the most important classes of complex molecules present in animal cells and tissues. Lipids serve a variety of functions: they supply energy for cellular processes, form cell membranes, participate in intercellular and intracellular signaling. Lipids are precursors of steroid hormones, bile acids, prostaglandins and phosphoinositides. Blood contains individual components of lipids (saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids), triglycerides, cholesterol, cholesterol esters and phospholipids. All these substances are not soluble in water, therefore the body has a complex system of lipid transport. Free (unesterified) fatty acids are transported in the blood as complexes with albumin. Triglycerides, cholesterol, cholesterol esters and phospholipids are carried by water-soluble lipoproteins. Some lipids are used to make nanoparticles, for example, in production of liposomes. The liposome membrane is composed of natural phospholipids, therefore liposomes have unique properties for drug delivery. They are nontoxic and biodegradable; furthermore under certain conditions they can be absorbed by cells, which facilitate intracellular delivery of their content. Liposomes are used for targeted drug delivery in photodynamic or gene therapy, and in other applications, e.g. in cosmetics.